Broadening of Er3+ electronic states in phosphate glasses

Absorption and emission spectra of Er3+-doped and Er3+-Yb3+-codoped phospha te glasses have been studied within the temperature interval from 10 to 300 K. The analysis of Er3+ Stark splitting for the excited state I-4(13/2) an d the ground-state I-4(15/2) multiplets is performed. Simulation of inhomog eneous broadening of Stark levels has shown that all (2J+1) components of b oth multiplets are split by random distortions of the initial symmetric pol yhedron, consisting of the neighboring oxygen ions in phosphate glasses. In homogeneous broadening of Stark levels is different for each energy level a nd reflects the sensitivity of a particular energy level to the variation o f crystal field. At least three energy levels participate in shaping the lo w-energy side of the emission spectra, caused by the I-4(13/2)--> I-4(15/2) transition. The emission linewidth corresponding to the transition to the highest by energy Stark component is assumed to derive from comparable cont ributions of inhomogeneous and homogeneous broadening, the latter caused by intra-multiplet transitions. The presence of the highest Stark level in th e crystal-field splitting of the ground-state I-4(15/2) manifold with a hig h rate of nonradiative relaxation is essential for writing the rate equatio ns which describe the laser operation of erbium glass lasers. (C) 2001 Amer ican Institute of Physics.